September 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
(3)Fischer, F., and Bendixsohn, K., 2. anorg. Chem., 61, 13, 153 (1909). (4) Fischer, F.,and Massenez, C., Zbid., 52,202,229 (1907). (5) Gable, C. M., Beta, H. F., and Maron, S. H., J. Am. Chem. SOC., 72,1445 (1950). (6)Grafenberg, 2.anorg. Chem., 36,355 (1903). (7) Kremann, Ibid., 36,403(1903). (8) Lash, E.I., Hornbeck, R.D.,Putnum, G. L., and Boelter, E. D.. J . Electrochem. Soc., 98,134 (1951). (9) Latimer, W. M., “Oxidation Potentials,” New York, Prentioe Hall, 1938.
(10)Maohu, W., “Das Wasserstoffperoxyd und die Perverbindungen,” Berlin, Springer Verl.. 1937.
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(11) McLeod, Chem. SOC.J . , 49, 591, (1886). (12) Malquori, G.,Attiaccad. naz. Lincei, 33,ii, 112-16 (1924). (13) Putnam, G., Moulton, R., Fillmore, W., and Clark, L., TTm8. Electrochem. SOC.,93,211-21 (1948). (14) Schonbein, Pogg. Ann., 50, 616 (1840). (15)Soret, Compt. rend., 56,390 (1863). (16) Targetti, Nuovo cimento, 10,360 (1899). (17) Thorp, C.E.,IND. ENG.CHEM.,ANAL.ED.,12,209 (1940). (18) Wartenberg, H., and Arohibald, E. H., 2. Electrochem., 17, 812 (1911). (19) Wulf, 0. R.,and Tolman, R. C., J. Am. Chem. Soo., 49, 1660. (1927). ACCEPTEDFebruary 4. 1H52
RECEIVED for review July 13. 1951.
Acid Composition of Gum Spirits of Turpentine and Low Wines E. D. PARKER AND L. A. GOLDBLATT Naval Stores Research Division, Naval Stores Station, Olustee, Fla, OMMERCIAL gum spirits of turpentine generally contain a certain amount of acidic materials whose presence may contribute t o the deteriorative changes that take place in the quality of turpentine during storage. The gum naval stores industry is interested in reducing the acidity of turpentine, especially since the Commodity Credit Corp. has placed a maximum limit on the acid content of turpentine (an acid number of 0.5) that is acceptable for a government loan. Consequently, some work of this laboratory has been directed toward solving the problem of turpentine acidity. T o aid in this work, through obtaining a better understanding of the causes and the prevention of acidity, the composition of the acidic components of gum spirits of turpentine was investigated. The acidic components both of low wines-the aqueous phase of turpentine distillation-and of turpentine tailings were studied. To obtain typical samples, low wines and turpentine from commercial distillations were used. I n preliminary work several methods for the analysis of organic acids were tested, including Duclaux numbers (%), analytical steam distillation by the method of Olmstead, Whitaker, and Duden ( 4 ) , the fractional extraction procedure of Bush and Densen ( I ) , and the chromatographic procedure of Ramsey and Patterson (5-7), and of Marvel and Rands ( 3 ) . The most useful were found t o be the procedure of Marvel and Rands and that of Ramsey and Patterson, the latter somewhat modified. These two, with the procedure of Bush and Denson ( I ) , were applied in the work reported. LOW WINES
Low wines of 0.018 N acid PROCEDURE FOR FRACTIONATION. concentration from a commercial still were made alkaline with an excess of sodium hydroxide and were concentrated by distillation to about 3% of the original volume. Five fractions of the sodium salts of this material were obtained as follows: A 10-liter sample was concentrated and saturated with carbon dioxide, and the precipitate was extracted with alcohol t o yield fraction 1. The filtrate was further concentrated and diluted with alcohol and acetone in a stepwise procedure, and the supernatant solution was finally evaporated t o dryness t o obtain fractions 2 through 5 . Each salt fraction wae acidified with sulfuric acid and the acids were separated by distillation in vacuo, The five distillates, or acid fractions (Table I), were obtained as concentrated aqueous
solutions, the per cent acid of the fractions ranging from 37 t o 43.6% (calculated as acetic acid). An over-all yield of 72% of the acids present in the original low wines was obtained. ACID CONCENTRATIONS. Averages of t h e concentrations of acetic and butyric acids, in the five fractions, roughy calculated on the basis of the multiple fractional extraction procedure of Bush and Densen (I), as a preliminary approach t o the problem, showed about 90% acetic and 7% butyric acids. A disadvantage with this method is that the values for acetic acid include any formic acid present. Fraction 5 was estimated t o contttin about 70% acetic acid and 30% butyric acid, disregarding t h r other minor constituents. T o determine more accurately the composition, a coniposite of the five acid fractions was prepared by mixing together a volume of each fraction proportional t o the total volume of that fraction, resulting in a mixture with the same composition as the total distillate. A part of this composite solution, 0.1 ml., was absorbed on a column of 20 grams of silica gel containing 12 ml. of water, and was developed with chloroform and butanol by the method of Marvel and Rands ( 3 ) . Titration of the effluent indicated 5% butyric and higher acids (peak effluent volume or P E V of 50 ml.); 0.2% propionic acid (PEV, 130 ml.); 88% acetic acid (PEV, 160 ml.); and 770 formic acid (PEV, 270 ml.). Fraction 5 , 0.1 ml., was chromatographed in the same way and was found to contain 29% butyric and higher acids (PEV, 40 ml.); 0.9% propionic (PEV, 110 ml.); 40% acetic (PEV, 160 ml.); and 30% formic acid (PEV, 260 ml.). The acids from formic t o butyric were studied by the proce\lure of Marvel and Rands (3). Butyric and the higher molecular weight acids were separated from fraction 5 by a modification of the Ramsey and Patterson
TABLEI. CONCENTRATED AQUEOUSACIDS OBTAINED FROM FRACTIONATED SODIUM SALTS Volume. Fraction M1. ’
1 2 3 4 6
402 55 72 44 104
Density, di4 1,046 1.054 1.049 1.044 1.037
Refractive Index, ng0
1.3623 1.3603 1.3595 1.3655 1.3627
Concn.,
N 7.62 7.47 7.31. 6.36 6.41
Total Acid (as Acid, Acetic), Equiva% lents
43.6 43.0 41.7 36.5 37.0
3.06 0.41 0.63 0.28 0.67
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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and 2 volumes of ether. The first ether phase, that having the highest content of the least water-soluble component, containing 23y0 of t h e acid, was titrated t o neutrality and evaporated to dryness. Part of t h e residual salt was used t o prepare the p phenylphenacyi ester ( 8 ) , which after recrystallization wa9 identical with the p-phenylphenacyl ester of n-butyric acid. One half gram of salt yielded 0.18 gram of derivative, melting point 76' t o 77" C. Although t h r presence of n-butyric acid was thus established, partition chromatograms showed that isobutyric acid was more abundant in t h e sample than n-butyric acid, by more than 2 t o I .
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Acids obtained from low wines (fraction 5) Mixture of caproic (28%), valeric (lo%), butyric (46%), and isobutyric (1670) acids
EXTRACTION OF ACIDS. A 13.8-liter sample of turpentine tadings of exceptionally high acid number, 5.80, from a commercial distillation, was extracted with 750 grams of 10% sodium hydroxide, and then with 200 ml. of water. The two extracts were combined and concentrated to 573 nil on a hot plate. After cooling, the alkaline solution was acidified with diluted sulfuric acid and the black oil which separated was extracted with ether. The ether extract was then extracted with 3% sodium carbonate solution. In this way the acids were removed from a small amount (2.64 grams) of phenolic material. The carbonate solution was acidified t o yield 11.7 grams of black oil (neutral equivalent 159). P a r t of this oil (7.40 grams) was distilled in vacuo (about 2 mm.) a t 85" t o 90' C., yielding 2 87 grams of distillate (neutral equivalent, 129).
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method. Silica gel, 20 grams, was impregnated with 12 ml. of methanol, and this material was slurried in iso-octane without adding an indicator. The slurry was packed in a chromatography tube in the conventional manner. A sample of fraction 5 (0.1 ml.) was then absorbed directly on the column and the acids were eluted with iso-octane. Fractions of the effluent, each 10 ml. or smaller, were collected, and each was titrated t o phenolphthalein end point with alcoholic alkali (about 0.025 N ) . Four components were indicated with peak effluent volumes and percentage compositions as follows: 130 ml., 3.2%; 190 ml., 1.5y0; 230 ml., 65 t o 70%; and 270 ml., 25 to 30y0 (the percentage is based on the acid eluted and not that placed on the column). The milliequivalents of acid per 10 ml. of effluent are plotted against volume of effluent in Figure 1 (curve A ) . The components have been tentatively identified as caproic, valeric, isobutyric, and butyric acids, on the basis of a partition chromatogram of known acids. An iso-octanestock solution (0.0167 X) was prepared, containing 28% caproic acid, 10% valeric acid, 4G% butyric acid, and l G % isobutyric acid. Two milliliters of this solution were eluted on a column with iso-octane (Figure 1, curve B ) . A stock solution of acid fraction 5, 2 ml. in 39 ml. of iso-octane, was prepared and dried over sodium sulfate. One milliliter of this solution was run on a column as usual and 5-ml. fractions were collected for titration (Figure 2, curve A ) . A stock solution (0.462 N ) containing 30% butyric and 70% isobutyric acids was prepared and 1.0 ml. of the solution run as usual on a chromatogram (Figure 2, curve B ) . Curves A and B in Figure 2 are very similar; thus, the ratio of butyric t o isobutyric acid is of the same order of magnitude. PREPARATIOK OF BUTYRICACID DERIVATIVE. T o obtain enough butyric acid t o prepare a derivative, fraction 5 was subjected to a 6-stage, diagonal-type extraction [36 extractions as described by Bush and Densen ( I ) ] ,between 1 volume of water
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Acids obtained from low wines (fraction 5 ) Mixture of butyric (30%) and isobutyric (70%) acids
The turpentine layer was washed again with 4 liters of water (several days were required for the two phases t o separate). The aqueous phase was acidified with diluted sulfuric acid t o yield a semiliquid precipitate. This material was taken up in ether and extracted with sodium carbonate solution. The ether on evaporation yielded 1.55 grams of phenolic material. The carbonate solution was acidified t o reprecipitate the acids which, after the supernatant solution was decanted off and washed with water, were taken up in acetone. T o remove resin acids from the precipitated acids taken up in acetone, the acetone was treated with 170 ml. of cyclohexylamine, and 346 grams of amine salts were obtained. Acidification of the amine salts produced 274 grams of resin acids (neutral equivalent 333).
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1952
The resin acid fraction (0.17gram) was dissolved in 10 ml. of isc-octane, and 2.0 ml. of the resulting solution (0.0521 N ) were chromatographed as before. The results, shown in Figure 3, curve D, indicate the sharpness of separation of the resin acids with a peak effluent volume of 30 ml., from the nonresin acids present. I
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Figure 3. Separation of Caproic and Higher Molecular Weight Acids o n Methanol-Impregnated Silica Gel Column by Elution with Iso-octane Acid fraction obtained from turpentine (neutral equivalent, 159) Mixture of caprylic (16%), heptanoic (36%), and caproic (47%) acids C. Second acid fraction obtained from turpentine (neutral equivalent, 160) D. Resin acid fraction obtained from turpentine
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The ether solution was extracted with 5% sodium hydroxide solution. The alkaline phase was then acidified with sulfuric acid and distilled. From the first 200 ml. of distillate 1.4 grams of immiscible oil (neutral equivalent, 162) were removed with a pipet; the bulk, together with the next 170 ml. of distillate, was extracted with ether t o yield 1.75 grams of additional oil (ng, 1.4556; neutral equivalent, 160). CHROMATOGRAPHIC STUDYOF ACIDS. Stock solutions in isooctane of three of these acidic materials (neutral equivalents of 160, 129, and 159) were prepared, and aliquots separated chromatographically on silica gel columns with methanol as the immobile phase and iso-octane as the eluent. Four components were found in each case. Three of these were found a t peak effluent
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volumes near those of caproic, heptanoic, and caprylic acids. The fourth occurred midway between the caprylic peak of 60 and the heptanoic peak of 90. One milliliter of a 0.0403 N solution of a known mixture of caprylic (16%), heptanoic (36%), and caproic acids (47%) in iso-octane was placed on a column and developed with isooctane. The effluent was collected in 5-ml. fractions and titrated with standard alcoholic alkali (Figure 3, curve B ) . A stock solution of the acid mixture (neutral equivalent, 159) was prepared by extracting 1.0284 grams of the sample with four 25-ml. portions of iso-octane and diluting the combined extracts to exactly 100 ml. This gave a n 0.0508 N solution. One milliliter of this solution was separated on a column, 2.5- and 5-ml. fractions being collected for titration (although these smaller fractions were titrated in some cases, the values plotted on the curves are milliequivalents of acid per 10 ml. of effluent). The data are plotted in Figure 3, curve A . About 86% of t h e acid placed on the column was found in the first 150 ml. of effluent. The sample with neutral equivalent of 160, 0.08 gram, was dissolved in 10 ml. of iso-octane, giving an 0.0366 N stock solution. Two milliliters of this stock solution were chromatographed in the usual way. Fractions (5 ml.) were collected and titrated. The results are shown in Figure 3, curve C. The titrated fractions were pooled roughly according t o band-Le., 40 to 70 ml. as band 1, 70 to 105 as band 2, and 105 t o 150 as band 3. The 40 to 70 band decolorized bromine water strongly, the 70 t o 105 band slightly, and the 105 t o 150 band not at all. Weighed samples (0.2 gram) of the acid fraction (neutral equivalent, 160) were placed in glass-stoppered flasks with 20 ml. of 0.1 N bromine solution (in methanol) and allowed t o stand in a refrigerator for 3 hours. At this time 15 ml. of 10% potassium iodide was added and the samples were titrated t o the starch end point with standard thiosulfate solution. The bromine numbers calculated from these data indicated 0.325 me. of unsaturation per milliequivalent of acid. Since band I of curve C (Figure 3) represents about 35% of the total acidity, it seems safe t o assume that this component is a n unsaturated acid with one double bond per molecule; however, the presence of a multiply unsaturated acid in the “shoulder” zone following band I is not ruled out by these data. LITERATURE CITED
(1) Bush, M.T. and Densen, P. M., Anal. Chem., 20, 121 (1948). (2) Duclaux, E.,“Traite de Miorobiologie,” vol. 3, p. 394, Paris, Manson and Cie., 1900. (3) Marvel, C. S., and Rands, R. D., Jr., J . Am. Chem. Soc., 72,2642 (1950). (4) Olmstead, W. H., Whitaker, W. M., and Duden, C. W., J . Bid. Chern., 85, 109 (1929). ( 5 ) Ramsey, L. L., J. Assoc. Oflc.Agr. Chemists, 31, 164 (1948). (6) Ramsey, L. L., and Patterson, W. I., Ibid., 28, 644 (1945). (7)Ibid., 31,139 (1948). (8) Shriner, R. L.,and Fuson, R. C., “The Systematic Identification of Organic Compounds,” 2nd ed., p. 132,New York, John Wiley and Sons, Inc., 1940. RECEIVED for review February 20, 1952.
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ACCEPTED April 19, 1952
